Offset-cutting tool



March l0, 1931. F. l. GETTY OFFSET CUTTING TOOL Filed oct. 18, 192s Mrs Patented Mar. 10, 1931 FRED I. GETTY, F JENNINGS, LOUISIANA OFFSET-CUTTING 'rooL Application lled October 18, 1928. Serial No. 313,283.

The invention relates tooffset cutting tools,

and has as an object the provision of an improved form of tool for cutting odset openings in the side of well casings.

; A further object of the invention is to pro-l vide an offset cutting tool in which the milling cutters have threaded engagement with annular enlargements formedupon lengths of ordinary drill stem'pipe.

It is a further object of the invention to provide an offset cutting tool in which the cuttersare adapted to operate and cut the ragged edges of the opening through the well 'casing without grabbing, thereby eliminating the danger of stopping the rotation of the drill stem and causing a breakage.

Further objects of the invention will appear from the following description when read in connection with the accompanying drawingsshowing an illustrative embodiment of the invention and wherein Figure l is a central section of a portion of a well casin showing the use of the tool which is the su ject-matter of the' invention.

Figure 2 is a side elevation of a portion of the cutting stem with milling cutters shown.

39 stem.

Figure 4 is a side elevation of a milling cutter, and

Figure 5 is a bottom plan view of the cutter shown in Figure 4.

As shown, the device is adapted to be used in the secondaryl operation of side-tracking wells. The primary operation consists in first setting a whipstock in the well casing at the proper depth, and then cutting an elongated slot or opening through the side of the well casing, by means of a milling tool attached to the lower end of the drill stem. The cutter rotating against the wedge-shaped surface of the whipstock as it passes down, is gradually Athe inside of the casing as at (13), and the -diverted outward through the well casing, so

as to make an opening as-stated.

The whipstock (11) loca-ted in the well casing (10) is shown as formed of two parts joined togethennas at (12); a construction which provides for convenience in transportation, although a single piece whipstock is v generally used in the smaller sizes.

The tool (11) is formed -to contact with lower end is formed to taper away from the casing at this point. A wedge (14) is showin which may be first placed in the casing, and the wedge surface thereof is then adapted to act on the end (15) of the tool (11') to force the point (13) against the inside of the casing and the upper .end (15') thereof against the opposite side of the casing.

` The opening in the well casing made by the primary operation as described above is unfinished and unsatisfactory Afor the purpose of sidetracking. As a rule said opening is comparatively short and irregular and the bottom end of the slit ends abruptly, due to the fact that the milling cutter does not follow and rotate against the surface of the whipstock the entire distance down to the point (13); but, breaks away from the cut and passes down outside the well casing, at some point above, which may be as much as two or three feet, thus leaving an abrupt shoulder, at the lower end which tends to give the drill stem a short bend or crook while drilling down through the opening, and rendering it unsafe for setting strainer, as there is great danger of a hang-up at this point when the screen is passing through.`

A secondary operation is therefore necessary to open up the slit, lengthen it out, correct its irregularities, and cut out the shoulder 85 at the bottom.' It is for this secondary opere ation that the present tool is designed. As shown in Fig. l, the tool comprises a cutter supporting stem (16) with cutters (24) and (25) mounted thereon. At the upper end of 90 the stem is a coupling member and at the lower end another coupling member (19). These couplings should be as large in diameter as will pass freely down through the well casing. The couplings serve as bearings for while milling out, it is not absolutely essential and may be dispensed within which case the drill bit (17) should be attached to the coupling (19).

In general practice the drill stem is removed from the well, after the first operation of milling and' then let down again with the proper mills for the second one, making two distinct operations in the job of sidetracking. It is however possible to combine the two by making the operation continuous. In such case the proper kind of mill for making an opening through the well casing is placed at the bottom end of the drill stem with the mills (24) and (25) mounted above. The

. lower mill for the primary operation could be mounted on the pipe (28) in place of the coupling (18) dispensing with the bit (17) or if preferred the length of pipe (16) can be discarded and the said mill mounted on the lower end of the stem (16). With such an arrangement the secondary milling could follow the primaryafter the first mill had cut though the well casing and passed down outs1 e.

In accordance with the inventiomthe tool is constructed by utilizing lengths of ordinary drill pipe which lengths may be joined by a flush joint (21), as shown in Fig. 3. Upon each length of the stem enlargements (22), (23) are formed, as by building metal thereon by the electric welding process or other means. The thus. formed enlargements are then externallyscrew threaded vfor engagement with the milling cutters (24), (25).

As shown in Fig. 2, the upper milling cutter is of a larger internal diameter than the lower thereof, by virtue of which fact the successive milling cutters can be passed over `the smaller enlargements each to position upon its own seat. By use of a joint (21),

between the location of each of the milling cutters, the internal diameter of the milling cutters may be all the same, the milling cutter being assembled with each joint before the joints are screwed together. Milling cutters for the purpose of the present invention have heretofore been provided with the ordinary straight tooth cut on the side and end. vIn such case a stili', heavy,

massive stem was employed as a mountin for supporting them. The stiffness and in exibilityV of the stem was depended on to hold the cutters against the work and force'them to out and trim the opening to its proper size and shape. Such tools were expensive and unsatisfactory as the cutters would frequently grab the ragged edges of the casing and break teeth from the mill. The present invention is designed to use a cutter'stem which is light and resilient, adapted to spring away from the out to some extent when said cut becomes too heavy. By mounting spiral side cut mills vthereon provision is made to .prevent the troubles heretofore experienced. In the operation of milling several teeth are in contact at all times and there is no opportunity for the ragged edges of the slit becoming locked between cutter teeth. The spiral mill teeth rotate against and scrape the edges of the pipe'and permit the stem to rotate freely, eliminating all danger of grabbing. While milling cutters with right hand spiral teeth may be used for some jobs, the

left hand spiral cut is preferable for the more difficult ones where underground conditions are bad.

Minor changes may be made in the physical embodiments of the invention within the scope of the appended claims without departing from the spirit thereof.

I claim:

1. An offset cutting tool comprising, in combination, a resilient tubular stem, a plurality of enlargements integrally formed thereon, and a milling cutter having screw threaded engagement with each of said enlargements.

2. An ofl'set -cutting tool comprising, in combination, a sectional resilient tubular stem, an enlargement formed integrally upon each of said sections, said sections having screw threaded engagement with each other, and a milling cutter having screw threaded engagement with each of said enlargements.

3. An offset cutting tool comprising, in combination, a resilient tubular stem formed in sections, said sections joined by flush screw threaded couplings, an integral enlargement carried by each of said sections, and a milling cutter having screw threaded engagement with each of said enlargements.

4. An offset cutting tool comprising, in combination, a resilient tubular stem having integral enlargements formed thereon, a milling cutter having screw threaded engagement with each of said enlargements, a bearing enlargement carried by said stem below the lowermost of said enlargements.

5. An oset cutting tool comprising, in combination, a tubular siem having integral enlargements formed thereon, a milling cutter having screw threaded engagement with each of said enlargements, a bearin enlargement carried by said'stem below t e lowermosty of said enlargements, the diameter of said stem and the thickness of its walls so chosen as to provide resilience of the stem whereby undue resistance to revolution by a v cutter may cause iexure of the stem and consequent retreat of the cutting edges from the work. I

6. An oset cutting tool comprising, in combination, a resilient tubular stem having integral enlargements carried thereby, a milllng cutter having screw threaded en agement with each of said enlargements, a aring enlargement carried by said stem above and below said milling cutters.

" FRED I. GETTY. 

